OK. I should have posted the guide right away it seems :lol:.
Anyway, as it's only possible to remove all posts of a single Guest_ member through ACP, I've had to do "open heart surgery" on the DB.
It is easy to find and manipulate with Guest_ members and their topics or posts, but I've done the actual deleting through IPB front end, so I wouldn't end up with any orphaned replies.
I've only wanted to remove the topics/posts from a single forum (with an ID of Y for the purpose of this guide), but the same procedure applies for deleting all Guest_ topics on the board.
Of course, before attempting to do this, backup your database!
1) Create a new temporary "Pruned Topics" forum and get its ID, that we will call X.
2) Go to phpMyAdmin and run this query:
UPDATE `ibf_topics` SET `forum_id` = 'X' WHERE `starter_id` ='0' AND `forum_id` = 'Y';
This will move all the topics (and associated posts) from the forum you want to clean up to the new Pruned Topics forum.
Should you want to move topics started by Guest_ members from ALL your forums, run this query instead:
UPDATE `ibf_topics` SET `forum_id` = 'X' WHERE `starter_id` ='0';
3) Go to ACP and Resynchronize the affected forums (or the whole board in the other case)
4) Empty your Pruned Topics forum either through ACP or by navigating to the forum and using Prune function
5) Enjoy your cleaned-up board :smile:.
That's it, I hope it helps someone out there and that it will become a standard option in IPB or at least that someone will make a hook for it.
Best regards, Nikica.